Seat belt webbing and method of dyeing same

ABSTRACT

A process of dying a seat belt within a dye range, the seat belt comprising a woven polyester material containing a blended hybrid fiber of the type known as PET-polycaprolactone diblock copolymer fiber, the process comprising the steps of: heating the webbing to a preferred range while under tension and subsequently washing, steaming, finish coating and drying the webbing.

BACKGROUND AND SUMMARY OF THE INVENTION

[0001] This is a regularly filed utility patent application claimingpriority of provisional patent application No. 60/214,193, filed Jun.26, 2000.

[0002] The invention generally relates to a method of dyeing aparticular type of seat belt webbing and more particularly to a methodof dyeing the blended hybrid fiber and the seat belt generallyidentified in U.S. Pat. Nos. 5,830,811 and 6,228,488, each of which isincorporated herein by reference. This blended hybrid fiber is of thetype known as PET-polycaprolactone diblock copolymer fiber.

[0003] The fiber has many uses. One such use is within a woven seat belt(webbing) comprising blended hybrid warp and blended hybrid or PET weftfibers. This particular blended hybrid PET fiber displays highelongation rate as compared to the elongation rate of a typicallyconstructed polyester seat belt webbing whose elongation is in thevicinity of 5-14 percent. In essence, this type of seat belt stretchesin a controlled manner, and absorbs energy while stretching, whichlowers the chest and head injury levels that are commonly associatedwith vehicular crashes and used as a measurement of the efficiency of asafety restraint system.

[0004] One significant disadvantage of this type of fiber, as well as aseat belt webbing made with this fiber, is that the dyed material is notcolor fast, light fast, is difficult to dye, and does not retain a softpliable consistency.

[0005] It is an object of the present invention to be able tosatisfactorily dye a blended hybrid fiber and more particularlypolyester/nylon hybrid seat belt webbing having such fibers.

[0006] Accordingly the invention comprises: a process of dying amaterial including seat belt webbing within a dye range, the material orseat belt comprising a woven polyester and containing blended hybrid PETfibers, the process comprising the steps of: heating the material(webbing) to a preferred range while under tension and subsequentlywashing, steaming, finish coating and drying the webbing.

BRIEF DESCRIPTION OF THE DRAWING

[0007]FIG. 1 shows a generally known dyeing range and process that isadaptable to dye seat belt webbing using synthetic fibers.

DETAILED DESCRIPTION OF THE INVENTION

[0008] The following method of dyeing is particularly suited for dyeingmaterial including seat belt webbing (also referred to as a seat belt orwebbing) containing a PET-polycaprolactone diblock copolymer fiber.

[0009] The general process of dyeing a woven polyester material,including seat belt webbing, with or without blended hybrid PET fiberuses common machinery and similar process steps. However, it wasdiscovered that simple and subtle changes in known processessurprisingly changed the characteristics of the dyed material (webbing)to an acceptable product. The following shows a prior art process fordyeing blended hybrid fibers; subsequently, the changes to this processare defined. It has been proposed to pass a PET seat belt (webbing) 10through a tensioning device to allow constant back tension of the beltprior to the dyeing process. Simply stated, there must be some tensionon the belt prior to immersion in the dye pad and pan itself to preventthe webbing from developing fold and crease marks. FIG. 1 shows agenerally known dyeing process that is adaptable to the presentinvention. The hybrid blend PET seat belt 10 is padded through a dyebath 20 (the dye bath liquid 22 will also be called liquor) potentiallyincluding but not limited to dyestuff (most often disperse dyestuff isused for coloring of the belt), acetic acid, dispersant, chelate, water,carrier, UV absorber and wetter (wetting agent). The liquor does notnecessarily have all the chemical components, which may vary fromprocess to process, but must have the colorant (dyestuff) to impart acontrolled color to the hybrid blend PET seat belt.

[0010] The webbing is then passed through a nip point (single ormultiple) 24 to squeeze off or otherwise remove the excess dye bathliquor to a relatively consistent amount. The liquor-saturated seat beltis then passed through a heated zone (or pre-drier) 30 with atemperature maintained below 143 C (290 F). At the completion of theheated zone the liquor has been reduced to chemicals not flashed(evaporated off by the heating) and the dyestuff. The seat belt 10 isnot dyed at this time but rather weakly stained by the dyestuff.

[0011] The seat belt is then passed through a tension device most oftencalled a brake unit 40, which may include a number of rollers and amotor and/or a brake to slow the speed of the rollers. The brake unitcan push or run excess seat belt to an oven 50, which is next in theprocess flow or can impart excess tension on the seat belt holding backthe webbing back from the preferred thermosol oven 50. This action ofthe brake unit 40 is one part of controlling the elongationcharacteristics of the material (webbing 10) on the thermosol dye range.

[0012] The seat belt now enters the oven 50, the oven for the dyeingprocess. In this prior method, the thermosol oven is heated to atemperature to allow the seat belt to reach 210 C (410 F). At the 210 C(410 F) temperature the fiber will soften and an attraction between thedisperse dyestuff and the polyester will allow the coloring of thewebbing to occur. Also at this temperature the softened polyester willbe restructured to a new width, thickness, and elongation based on thestretch or over feed of the brake unit 40 and haul unit 60 (the haulunit is further in the process flow and includes for example a motor androllers). Temperatures of this process are not necessarily absolutely210 C (410 F). The past practice of dyeing PET seat belt has been in therange of 199 C to 232 C (390 F to 450 F). At temperatures below 199 C(390 F) the PET is very hard to adequately dye and control elongationand at temperatures above 224 C (435 F) the PET tends to weaken andshine.

[0013] In the prior process, upon exit of the thermosol oven, the seatbelt enters a water quench unit 70, which may be a spray or bath. Thewater quenching has a twofold purpose of aiding in setting theelongation by flash cooling the seat belt and also begins the washingprocess. However, in the present invention this step must be eliminated.A drain 72 may also be provided. The seat belt does not have a 100%affinity for the disperse dyestuff and of the remaining dispersedyestuff 5-15% must be removed to allow the seat belt to be utilizedwith out fear of failing dye stability or crock tests.

[0014] The seat belt next enters the haul unit 60. The haul unit acts inconjunction with the break unit 40 to impart tension on the seat belt.This tension is the means of controlling the elongation of the seat beltwebbing. The haul unit is the lead motor on the dye range and istherefore the speed determining step of the dye range.

[0015] The seat belt next enters the scour pad 80. In the scour pad theseat belt is exposed to a scour mix. This scour mix can contain soaps,wetters, dispersants, alkali, water, and reducing agents. The scour mixdoes not have to contain all the mentioned chemicals and typically doesnot contain all the chemicals at the same time. The seat belt picks up5-20% by weight of the scour mix from the pad after passing through thescour pad nip 82.

[0016] The seat belt next enters a steamer chest. The steamer chest 90can be used solely to control the dwell time to allow the scour mixappropriate time to penetrate the web and loosen the unfixed dyestuff.The steamer chest can also be used to heat the web/scour mixture topromote the cleaning of the web. The steamer can be used to increaseelongation of the web if the steam temperature is in the range of 93C-104 C (200-220 F).

[0017] The seat belt is now washed in a washer 100. This processinvolves allowing the web to be immersed or sprayed (see 70 a) withwater in repetitive actions. Between each action a vacuum 102 extractionof the web or a pinching 104 of the web occurs to force the excess waterand unattached dyestuff from the web. This process can be run either hot(typically heated with steam, see heater 106) or cold. Heated washingcan increase elongation marginally but will also improve washingefficiency.

[0018] The seat belt is now dried. The drying action can be accomplishedby steam conduction, infrared drying or heated air convection (numeral110 shows a dryer). If the seat belt is formed from twisted warp yarnthe dyeing process can be completed at this time. If the seat belt isformed from untwisted warp yarn the seat belt may require the additionalprocesses of a protective over-coating and subsequent drying. The dryingaction is to dry the web to a point of dryness at least equal to theabsolute moisture level at ambient atmospheric conditions of at ambienttemperature.

[0019] The seat belt, if untwisted warp yarn is used, next enters afinish application 120. The finish is typically a compound or mixtureincluding but not limited to a wetter, mineral oil, ester or esters,water, and binders, which is available in differing forms from differentmanufacturers. The finish is applied to untwisted yarn to protect theyarn in abrasion conditions. The finish acts as a lubricant for the seatbelt to reduce friction between the belt and any surface the beltcontacts.

[0020] The seat belt, if untwisted warp yarn is used and the previouslydescribed finish pad step occurs, next enters a final drier 130. Thefinal drier is used to remove all excess moisture, from the belt, to theabsolute moisture level or below the absolute moisture level found atambient atmospheric conditions. The final drier 130 can be eitherinfrared drying, conductive drying, or convective drying.

[0021] The present invention refines the process and procedures toproduce a material, including an occupant safety seat belt, of thePET-polycaprolactone diblock copolymer yarn. As a seat belt this productmeets federal occupant requirements outlined in FMVSS 209. Attempting toprocess the PET-polycaprolactone diblock copolymer fiber under standarddye range conditions, such as outlined above, will not produce anacceptable occupant safety seat belt. The belt will be extremely stiffdue to the polycaprolactone component of the fiber melting andresetting. The present invention involves the adjustments to theoperation of the dye range to allow the webbing to be processed in sucha means as to allow a controlled product that meets FMVSS 209requirements.

[0022] The seat belt webbing 10 has the following generalcharacteristics. The belt comprises about 300-440 warp yarn ends of thePET-polycaprolactone diblock copolymer multi-filament fibers. The deniercan be in the range of 1000-1500. The end count and denier will varydepending on strength required by the customer. The fill fiber is aconventional polyester used in seat belts having a density of about15-20 picks per inch depending on pliability desired. The fill yarndenier can vary between 220 to 840 dependent on the desired thickness ofthe webbing.

[0023] The preferred method to produce PET-polycaprolactone diblockcopolymer seat belt webbing is as follows: The dye range is modifiedfrom industry accepted PET production setup. The thermosol temperature(see oven 60) is set at 149-167 C (300-330 F) vs. 199-235 C (390-455 F);this gives a maximum exposed operating temperature for the web 10 in therange of about 133-149 C (280-300 F) and preferably 143 C (290 F)(compared to the prior art of 210 (410 F)). To achieve this preferred290 F temperature the oven can be heated in the range of about 149-167 C(300-330 F). The dye range speed is slowed to allow the material todwell in the over (thermosol dwell) to be three-five (3-5) minutesinstead of the normally used 3 minutes. The steamer 90 is run with atemperature range of 99-105 C (210-220 F). Preferably the dwell time inthe steamer is about 2-4 minutes. The wash boxes 106 are run withtemperatures between 60-99 C (140-210 F). The thermosol quench 70 isturned off, which permits the disperse dye that is on the fiber to notbe reallocated unevenly prior to the dyeing of the caprolactonecomponent of the fiber in the steamer. The dye range is run with thehaul unit 2.5-7.0% faster than the brake unit imparting stretch to theseat belt webbing while in the oven.

[0024] The dye range dye mix formulation (applied at 20) is adjusted asfollows. A blended aromatic solvent and an organic ester compound suchas a monooelate ester carrier is added to the dye bath at 2% by volume.Both a photo stabilizer based on copper complex and achlorobenzotriazene UV absorber are used in conjunction with the solventthe ester compound. Both UV absorbers can be used up to 5% of the bathdependent on depth of shade and required lightfastness. The dye mix canalso contain 20% of a polyester resin fatty acid derivative overcoat.

[0025] The scour mix (applied at 80) is a mild surfactant formulation isadjusted as follows. A monooelate esters and organic compound carrier isadded to the scour mix at 2% of volume.

[0026] The final, water resistant, overcoat (applied at 120) is aperflouroalkylcopolymer emulsion finish.

1. A process of dying a seat belt with a dye range, the seat beltcomprising a woven polyester material containing PET-polycaprolactonediblock copolymer fiber, the process comprising the steps of:introducing the webbing into an oven under tension in the range of about138-167 C (280-330 F).
 2. The process as defined in claim 1 wherein thetension of the webbing within the oven is obtained by a step of:controlling the relative speed of one of a brake and a haul unit,wherein the haul unit operates at about 2-7% faster than the brake unit.3. The process as defined in claim 1 wherein the dwell time of anyparticular length of seat belt in the oven is about 3-5 minutes.
 4. Theprocess as defined in claim 1 wherein after the seat belt webbing exitsthe oven, it is washed and then steamed wherein the temperature within asteaming unit is in the range of about 99-105 C (210-220 F).
 5. Theprocess as defined in claim 1 wherein the webbing is not quenched whileit is within or adjacent to the oven, which is a thermosol oven.
 6. Theprocess as defined in claim 1 including the step of submersing thewebbing within a dye bath comprising a 2% solution by volume of blendedaromatic solvents and monooelate esters carrier.
 7. The process asdefined in claim 6 wherein the step of submersing the webbing within adye bath includes immersing the webbing in a solution containing a photostabilizer based on copper complex and a chlorobenzotriazene UVabsorber.
 8. The process as defined in claim 6 wherein the step ofsubmersing the webbing within a dye bath further includes a step ofimmersing the webbing in a solution containing a polyester resin fattyacid derivative overcoat in the dye mix.
 9. The process as defined inclaim 1 including the step of introducing the webbing to a scour unithaving a scour mix of at least 2% monooelate ester carrier.
 10. Theprocess as defined in claim 1 including the step of passing the webbingthrough a terminal dryer and subsequent to drying applying an overcoating to the webbing comprising a perflouroalkylcopolymer emulsionfinish.
 11. A process of dying a seat belt within a dye range, the seatbelt comprising a woven material containing a blended hybrid fiber ofthe type known as PET-polycaprolactone diblock copolymer fiber, theprocess comprising the steps of: heating the webbing to a preferredrange while under tension and subsequently washing, steaming, finishcoating and drying the webbing.